1. Technical Field
The present invention relates to a vehicular suspension system, and more particularly, to a double wishbone type suspension system for driving wheels of a vehicle.
2. Related Prior Arts
An exemplary double wishbone type suspension system for driving wheels is disclosed in Japanese Patent Application Laid Open No. Toku-Kai-Hei 2-249712 as illustrated schematically in FIG. 5 and FIG. 6. The suspension system comprises a wheel 31 driven by a drive shaft 38, an axle housing 32 supporting the wheel 31, an upper arm 33 extending transversely in the vehicle from its inner ends pivotably connected with a body of the vehicle to its outer end pivotably connected with the axle housing 32, lateral links 34 (front) and 35 (rear) extending transversely in the vehicle from their inner ends pivotably connected with the body of the vehicle respectively to their outer ends pivotably connected with lower portions of the axle housing 32 respectively, a trailing link 36 with its one end pivotably connected to a lower portion of the axle housing 32 and with its another end pivotably connected to the body of the vehicle, a shock absorber 37 with its upper end mounted by a body flame of the vehicle and with its lower end pivotably connected to the rear lateral link 35, thus the assembly of the axle housing 32 and the wheel 31 being swingable up and down relative to the vehicle body when the wheel 31 bounds or rebounds.
In the abovementioned suspension system, since the trailing link 36 is needed to be arranged so as to connect its one end with the axle housing at a portion thereof adjacent to the drive axle 38, it is inevitable that the front lateral link 34 and the trailing link 36 cross each other in the plane view and consequently both these links must be arranged with a substantially large space therebetween in order to avoid interference with each other. Because of this, the front lateral link 34 is needed to be disposed at a relatively high position and consequently there is no room in the vertical direction for accommodating the shock absorber between the front lateral link 34 and the body flame. Thus, in this prior art the shock absorber 37 is mounted on the rear lateral link 35. Generally in this case, the rear lateral link 35 is connected with the axle housing 32 at a portion adjacent to the drive axle 38, that is to say, the distance between the supporting point of the rear lateral link 35 and the drive axle 38 is determined to be as small as possible, in order to decrease a moment around the axle 38 of the reaction force applied from the shock absorber 37.
However, mounting the shock absorber on the rear lateral link as disclosed in this prior art provides a disadvantage in a turn running performance of the vehicle. Namely, when the vehicle turns a corner, the toe angle of the wheel 31 tends to change in a toe-out direction by the large component of the cornering force applied to the rear lateral link 35 because of the relatively small distance between the drive axle 38 and the connecting point of the rear lateral link 35 with the axle housing 32.
Further, in the prior art there are difficulties in securing a camber angle and a tread rigidity because of the front lateral link arranged at a relatively high position.